Computer aided engineering (CAE) has been used for supporting engineers in many tasks. For example, in a structure or engineering product design procedure, CAE analysis, particularly finite element analysis (FEA), has often been employed to predict structural behavior (e.g., stresses, displacements, etc.) under various simulated loading conditions (e.g., static or dynamic).
FEA is a computerized method widely used in industry to numerically simulate (i.e., model and solve in a computer system) engineering problems relating to complex products or systems (e.g., cars, airplanes, consumer products, etc.) such as three-dimensional non-linear structural design and analysis. FEA derives its name from the manner in which the geometry of the object under consideration is specified. The geometry is defined by elements and nodal points. There are a number of types of elements, solid elements for volumes or continua, shell or plate elements for surfaces and beam or truss elements for one-dimensional structural objects. The geometry of each element is defined by nodal points, for example, a brick or hexahedral element comprising eight corner nodes.
An example of using FEA is sheet metal forming, which has been used in the industry for years for creating metal parts from a blank sheet metal, for example, automobile manufacturers and their suppliers produce many parts using sheet metal forming.
One of the most used sheet metal forming processes is deep drawing, which involves a hydraulic or mechanical press pushing a specially-shaped punch into a matching die with a piece of blank sheet metal in between. Exemplary products made from this process include, but are not limited to, car hood, fender, door, automotive fuel tank, kitchen sink, aluminum can, etc. In some areas of the die, the depth of a part or product being made is generally more than half its diameter. As a result, the blank is stretched and therefore thinned in various locations due to the geometry of the part or product. The part or product is only good when there is no structural defect such as material failure (e.g., cracking, tearing, wrinkling, necking, etc.). In order to produce a part free of these defects, it is critical to design an addendum section between the product design and the binder region.
In order to properly simulate metal necking failure in finite element analysis, a failure criteria is specified by users of FEA. Prior art approaches have been developed from physical metal specimen testing using average strain around the neck in metal necking failure, for example, data obtained basing on average strain measured with strain gauges. As a result, users need to specify a set of metal necking failure criteria that are finite element mesh (element dimension) dependent. These prior art approaches often cause confusions and difficulties for preparing input data and lead to incorrect simulation because users would need to prepare the failure criteria based on these artificial and ad hoc requirement. It would therefore be desirable to have methods and systems for specifying mesh size independent metal necking failure criteria in finite element analysis.